The invention relates to a magneto-optical light modulator, comprising a light source, a polarizer, an analyzer, a substrate, which on a first side supports a Faraday rotation layer. The Faraday rotation layer is positioned between the polarizer and the analyzer, and has having a plurality of modulation elements. Electronic means are provided for switching the magnetization state of selected modulation elements of the Faraday rotation layer, which elements undergo the Faraday effect dependent on their magnetization state, by which effect the polarization plane of a light beam produced by the light source and transmitted through the layer is rotated. The Faraday effect is defined as the phenomenon in which the plane of polarization of linearly polarized light is rotated into the direction of magnetization when it passes through a magnetic substance.
The theoretical background of magneto-optical light modulators or light switches, is described in Applied Optics, 7, 1968, pp 2432-2433, while a more detailed description of light modulators of the present type can be found in German patent application Publication No. 26 06 596. The present invention provides switchable thin-layer elements which are supported on a substrate whose magnetization state can be selectively switched electronically by a thermomagnetic switching method.
The magnetization state can be made visible as a bright-dark distribution via the Faraday effect, so that the present light modulator may be used for the optical display of data as an electronically switchable transparency. Once a given magnetization state has been produced, it remains stored for an indefinite period of time (bistable switching method) but it can also be switched as often as may be desired.
It is the object of the present invention to use the magneto-optical components for the spatial light modulation of dichroic light for a coloured display of data by a suitable use of the spectral properties of the modulation elements, in which the colour selection and the colour modulation can be carried out with each individual modulation element simultaneously for both colours.